Recirculating Heaters and Hospital Construction

Make-Up Air System vs. Recirculation Open Flame Heat

Problem: It has been stated that recirculation heaters save fuel cost vs. mechanical make-up air systems.
And, with built-in thermostats, recirculation heaters properly control the building conditions.

Outline of Project:

  • Midwest hospital project. Heated through the winter of 2012 – 2013
  • 7-story addition, plus basement with 20,000 sq ft each floor, for a total of 160,000 sq ft
  • Fuel source is natural gas and 5-lbs pressure
  • Building was split between east and west wings
  • Construction heating located as follows:
    • 70,000 sq ft (Floors 1 – 7)
    • 40,000 sq ft (Floors 1 – 4)
    • 20,000 sq ft
    • Total building area to be heated is 130,000 sq ft.
  • West side general schedule: Outer skin mid-December with permanent window January.
  • East side general schedule: Outer skin end of December with permanent windows end of January
  • Temporary windows installed into all openings as of November, 2012

Recirculation Heater - Contractor Promise:

  • 9 recirculation heaters to complete construction heat requirements: $ 9,000.00
  • Estimated fuel cost for using recirculating heaters: $ 30,000.00

Final Outcome - Using Recirculating Heaters:

  • 14 recirculation construction heaters required to heat the building throughout the winter season
  • Estimated end fuel cost, December thru mid-April ... $ 81,296.00 (meter start # 0000 / meter ending # 86,351)
    (Difference paid by customer of $ 51,296 .00 in extra fuel vs. quoted budget at start of project)
  • Temperature and humidity readings taken inside the project in March as example
    • Outdoor readings 28.0°F, 46.0 % RH
    • East wing readings (average) 50.0°F, 37.0 % RH * High RH area reading of 45 % RH
    • West wing readings (average) 32.0°F, 53.5 % RH * High RH area reading of 59 % RH
    • Central readings (average) 57.0°F, 35.0 % RH * High RH area reading of 56 % RH

What Could Have Been a Different Experience by Investing in Mechanical Make-Up Air Design ?

  • 3 Mechanical make-up air construction heaters could have provided heat for the entire project
  • Mechanical make-up air heaters would have been located outside building vs. Fourteen (14) open flame,
    recirculation style heaters and associated temporary fuel hoses laying throughout the work space.
  • Customer could have been provided with an up-front, realistic value of $ 80,000 - $90,000 for fuel costs
  • Superior control over building temperature and humidity vs. recirculation heaters. As recorded, 78% swings for
    average temperature and 51% RH swings for humidity levels throughout the inside of the building.
    Mechanical make-up air designs hold a more constant even interior temperature and RH humidity with recorded averages of 38% - 44%. (20% lower moisture average RH vs. recirculation)
  • Building materials perform better and final finish schedules stay on target when more control is provided
    by the use of a properly designed mechanical make-up air system vs. recirculation open flame heat